Marvelous Marvin Hagler (born Marvin Nathaniel Hagler; May 23, 1954) is an American former professional boxer who competed from 1973 to 1987. He reigned as the undisputed middleweight champion from 1980 to 1987, making twelve defenses of that title, and today holds the highest knockout percentage of all undisputed middleweight champions, at 78%. At six years and seven months, his reign as undisputed middleweight champion is the second longest of the last century, behind only Tony Zale, who reigned during World War II. In 1982, annoyed that network announcers often did not refer to him by his nickname, "Marvelous", Hagler legally changed his name to Marvelous Marvin Hagler.
Hagler is an inductee of the International Boxing Hall of Fame and the World Boxing Hall of Fame. He was named Fighter of the Decade (1980s) by Boxing Illustrated magazine, and twice named Fighter of the Year by The Ring magazine and the Boxing Writers Association of America (BWAA). In 2001 and 2004, The Ring named him the third greatest middleweight of all time and in 2002 named him the 17th greatest fighter of the past 80 years. The International Boxing Research Organisation (IBRO) rates Hagler as the sixth greatest middleweight of all time, while BoxRec rates him the sixth best middleweight of all time. Many analysts and boxing writers consider Hagler to have one of the best chins in boxing history.